The invention relates to active acoustic attenuation systems, and more particularly to a multi-channel system for a correlated input acoustic wave. Correlated means periodic, band-limited, or otherwise having some predictability. The invention arose during continuing development efforts relating to the subject matter shown and described in commonly owned co-pending application Ser. No. 07/691,557, filed Apr. 25, 1991, incorporated herein by reference.
The invention of the noted co-pending application arose during continuing development efforts relating to the subject matter shown and described in U.S. Pat. No. 4,815,139, incorporated herein by reference. The invention of the noted co-pending application also arose during continuing development efforts relating to the subject matter shown and described in U.S. Pat. Nos. 4,677,676, 4,677,677, 4,736,431, 4,837,834, and 4,987,598, and allowed applications Ser. No. 07/388,014, filed Jul. 31, 1989, and Ser. No. 07/464,337, filed Jan. 12, 1990, all incorporated herein by reference.
Active acoustic attenuation or noise control involves injecting a canceling acoustic wave to destructively interfere with and cancel an input acoustic wave. In an active acoustic attenuation system, the output acoustic wave is sensed with an error transducer such as a microphone which supplies an error signal to an adaptive filter control model which in turn supplies a correction signal to a canceling transducer such as a loudspeaker which injects an acoustic wave to destructively interfere with the input acoustic wave and cancel same such that the output acoustic wave or sound at the error microphone is zero or some other desired value.
The invention of the noted co-pending application provides a generalized multi-channel active acoustic attenuation system for attenuating complex sound fields in a duct, large or small, a room, a vehicle cab, or free space. The system may be used with multiple input microphones and/or multiple canceling loudspeakers and/or multiple error microphones, and includes a plurality of adaptive filter channel models, with each channel model being intraconnected to each of the remaining channel models and providing a generalized solution wherein the inputs and outputs of all channel models depend on the inputs and outputs of all other channel models.
The present invention provides a generalized multi-channel active acoustic attenuation system for attenuating complex correlated sound fields in a duct, large or small, a room, a vehicle cab, or free space. The system may be used with multiple canceling loudspeakers and/or multiple error microphones, and includes a plurality of adaptive filter channel models having model inputs and error inputs from error transducers, and model outputs outputting correction signals to output transducers to introduce canceling acoustic waves. The system has numerous applications, including attenuation of audible sound, and vibration control in structures or machines.